The parents of a severely autistic boy have been arrested after California police determined the 11-year-old had been kept in a cage.

Authorities said the metal cage - similar to an extra-large dog kennel - was found in the couple's home in Anaheim with a mattress and other bedding inside.

It was roughly 6ft (1.8m) tall, 5ft (1.5m) long and about 4ft (1.2m) wide with room to stand.

Image Caption:Loi Vu, 40 (L), and Tracy Le, 35.

The boy was not inside when police went to the house.

But family members gave investigators varying accounts of how long he had been kept in it, ranging from hours to days, police Lieutenant Bob Dunn said.

He said early indications were that the family might have been having difficulty coping with the boy.

"It appeared that as he grew older his episodes of violence and outbursts were increasing and perhaps the parents utilised the cage as a tool to modify that and to contain him when that was happening," he said.

The boy's parents, identified by police as Loi Vu, 40, and Tracy Le, 35, were held on suspicion of felony child endangerment and false imprisonment.

Image Caption:A mattress was found inside the cage

Officers went to the Anaheim home and arrested the parents after an anonymous tipster called Orange County Child Protective Services.

The child was well-nourished and appeared otherwise healthy and his two siblings, ages eight and 10, were also unharmed.

They were all placed in protective custody.

The parents, of Vietnamese origin, speak limited English, and investigators were using translators to sort out details in the case.